Leuco vat dyestuff paste for printing cloth



and especially of an, alkali than are commonly.

Patented June 23, 1936 2.045.477} LEUoo w rrnmsrm-F PASTE FOB Carl'Krauss, Franklort-on-the-Main-Iechenheim, and Alfred Hagenbiicker,Frankfort-onq the-Main-Hochst, Germany, assignors to Gen eral AnilineWorks, Inc.,' New York,'N. Y., a

corporation of Delaware pplication July 31,1931, Serial No.

No Drgwing A 54,380. In Germany August 6, 1930 7 Claims.

dyestufi pastes Ior printing cloth.

7 We have found'that vat dyestuflf pastes espe cially suitable forprinting cloth and possessing.

valuable properties are obtainable by mixing the stable leuco compoundsof certain'vat-dyestufis of the thioindigoid series obtainable accordingto U. S, patent application Serial No. 441,720, filed April 4, 1930, inthe name of CarlKrauss and Alfred Hagenbiicker, for -New stablereduction compounds of the thioindigoid. series and a process ofpreparing them with ferrous sulfate or other heavy-metal salts.According to that application, stable leuco compounds are obtainable,for instance, by treating a thioindigoid dyestuffwhich is substituted byat least one substituent of the group consisting of halogen, alkyl andalkoxy, with a reducing agent in the presence of an alkali andthereupon, if necessary, treating the reaction' mixture with an aciduntil the alkaline reaction to phenolphthalein paper has disappeared. Incertain cases the stable v leuco compounds are ,formed by treating thethioindigoid dyestuff with considerably smaller quantities of reducingagent used in preparing a vat of the dyestufl in question, whereby thestable leuco compounds are obtainable directly without using any'acld,i. e., they separate directly from the reaction mixture. In

case itis necessary to use larger quantities of the reducing agent andof the alkali, the sepa-, ration of the stable leuco compoundsfrom thereaction mixture is advantageously completed as.

described above, by adding to the reaction mixture an acid until thealkaline reaction-to phenolphthaleine. paper has disappeared.

The stable leuco compounds used in accordance with the present inventionare not identical with the normal leuco compounds ofvat dyestuffshitherto. known. The stable .leuco compounds are dimcultly soluble inalkalies and are stable to air and oxygen, that is to say, the stableleuco compound does not oxidize by the mere 111-.

fluence of air whereas, as it is known, the normal, hitherto known leucocompounds are soluble in alkalies and re-oxidize under the influence ofY air to the dyestufls proper. The stable leuco compound yields printsin the usual'way butalso with a considerably smaller quantity of areducing 0 agent than isrequired m the case or the dye- 'stufl proper.The thioindlgoid dyestuffs which are particularly suitable for thepurpose of the present invention are those corresponding wit thefollowing generaliormula:

. x I I 7 he present invention relates to new leuco vatiron salts. Theoxides or.

(01. 8-6) wherein X represents hydrogen or an alkyl group,

Y represents halogen, and R stands for an aromatic nucleus bound in twoadjacent positions,

especially a benzene nucleus, which may be substituted, i. e. suchsymmetrical or assymmetrical dyestufis oithe thioindigoid series as haveat least on one side a nucleus 'being'substituted either inthe fiposition by halogen or in the 4-position by alkyl and in the 6-positionby halogen. Such dyestuffs are, for instance, 6.6-dichloro 4.4dimethylthioindigo, 6.6 dichlorthioindigo.

v6.6'-dichloro-4'-methylthioindigo and 4.4-di---methyl-6.5.7'-trichlorthioindigo.

.Instead of ferrous" sulfate one can use other heavy-metal salts such assal s of zinc, or other droxides or the heavy-metals have a similareflfe'ct. I

In order-to obtain a homogenous paste which does not settle and toincrease the printing ca pacity of the leuco vat-dyestufi paste, it isadvisable in many cases to add glycerol, glycol, dihydroxydiethylsulfide, dihydroxydiethylene oxide or another agent of like effect tothe aqueous paste containing the heavy metal. To increase further thetechnical effect it is sometimes advisable to add the sodiumsaltofbenzylsultanilic acid or another hydrotropical agent of similaraction.

The new leuco vat-dyestufl. pastes are distinguished-by their goodcapacity for being fixed, and-for printing purposes they are veryeconomical in use.

A similar eflect canalso be obtained with mixtures of leucovat-dyestuffs in which the stable leuco compound of a dyestufl of thedefined class; 3

constitutes a considerable proportion.. .It is a surprising fact thatinthe new leucopreparations the stable leuco compounds, even when storedfor a prolonged time, are not materially re-oxidized into thecorrespondin", vat- ;dyes tufis and that, even if a re-oxidation shouldoccur input, the preparations have still an appreciable industrial;advantage over the prepara-' tions directly made from the vat dyestuiis.

The following examples serve to illustrate the invention but they arenotintended to limit it thereto, the parts being by weight:

(1) 13' parts of-the stable leuco compound or6.6-dichloro-4.4'-dimethylthioindigo, obtainable,

'.f0r instance, according to Example 2 of the co pending applicationSerial No. 441,720 filed'on April 4, 1930, in the name of Carl KraussandAlired Hagenbdcker, are mixed with about 2.4 parts of, crystallizedferrous sulfateand made up with water to 100 parts. By addition oiftheiron salt both the ease with which the stable leuco compound can behated and the economy in its use, which without the addition are alreadyconsiderable, are considerably enhanced.

4 annu leilect can be attained by adding fer-p0 rous sulfate to thestable leuco compound of 6.6- dichlorothioindigo and6.6'-dich1oro-4'methylthioindigo.

(2) 13 parts of the stable leuco compound of6.6-dichloro-4.4'-dimethylthioindigo as used in Example 1 are mixed with2 to 2.4 parts'of crysagent than is required in the case of the dyestufitallized ferrous sulfate and 30 parts of commercial glycerol and thewhole is made up with water to 100 parts. The mixture is distinguishedby the ease with which it can be fixed and its economy in use whenapplied to printing Durposes.

(3) In a manner similar to that of Examples 1 and 2, a considerabletechnical eflect may be obtained in the case of a mechanical mixture of6.6'-dichloro-4.4'-dimethylthioindigo and of 6.6- diethoxythioindigo byadding to its stable leuco paste ferrous sulfate or another heavy metalsalt and, if desired, any other of the'substances mentioned above.

We claim;

1. As new compositions of matter, dyestufl pastes containing a compoundof the group consisting of salts, oxides and hydroxides of iron, andzinc, and a stable leuco compound of a thioindigoid dyestufi of thefollowing general formula:

wherein X represents hydrogen or an alkyl group,

Y represents halogen and R stands for an aromatic nucleus bound in twoadjacent positions, said pastes being especially adapted for printingpurposes, said stable leuco compound being stable to air and oxygen,diilicultly soluble in alkali and yielding prints in the usual way butalso with a considerably smaller quantity of a reducing agent than isrequired in the case of the dyatui! proper.

2. As new compositions of matter, dyestuffpastes containing a compoundof the group con-- sisting of salts, oxides and hydroxides of iron, andzinc, and a stable leuco compound of the dyestufl of the followingconstitution:

yielding prints in the usual way but also with a considerably smallerquantity of a reducing proper.

' 3. As a new composition of matter, the dyestufl paste consisting ofabout 2.4 parts of crystallized ferrous sulfate, about 13 parts of thestable leuco compound .of, 6.6- dichloro-4.4'-dimethylthioindigoandabout parts of water, said paste having a good capacity for beingfixed and being very economical in use for printing purposes.

4. As a new composition of matter, the dyestuii paste consisting ofabout 24.4 parts of crystallized ferrous sulfate, about 30 parts ofglycerol, about 13 parts of the stable leuco compound of6.6'-dichloro-4.4'-dimethyl-thioindigo and about 55 parts of water, saidpaste having a good capacity for being fixed and being very economicalin use for printing purposes, said stable leuco compound being stable toair and oxygen, dimcultly soluble in alkali and yielding prints in theusual way but also with a considerably smaller quantity of a reducingagent than is required in the case of the dyestufl properl 5. As newcompositions of matter, dyestuif pastes containing a compound of thegroup consisting of salts, oxides and hydroxides of iron and zinc, and astable leuco compound of a thioindigoid dyestuil' of the followinggeneral formula:

wherein x represents hydrogen or an alkyl r up. Y represents halogen andR stands for a benzene nucleus bound in two adjacent positions, saidpastes being especially adapted for printing purposes, said stable leucocompound being stable to air and oxygen, difllcultly soluble in alkaliand yielding prints in the usual way but also with a considerablysmaller quantity of a reducing agent than is required in the case of thedyestufl proper.

6. As new compositions of matter, dyestuii pastes containing a compoundof the group consisting of salts, oxides and hydroxides of iron andzinc, the sodium salt of benzyl-sulfanilic acid and a stable leucocompound of a thioindigoid dyestufi of the following general formula:

E 3*]. ,.L=L I wherein x represents hydrogen or an alykyl up, Yrepresents halogen and R stands for a benzene nucleus bound in twoadjacent positions,

said pastes being especially adapted for printing purposes, said stableleuco compound being stable to air and oxygen, difiicultly soluble inalkali and yielding prints in the usual way but'also with a considerablysmaller quantity of a reducing agent than is required in the case of thedvestufl' proper.

7. As new compositions of matter, dyestuff pastes containing ferroussulfate, the sodium salt of benzyl-sulfanilic acid and the stable leucocompound of 6.6'-dich1oro-4.4'-dimethylthioindigo, said pastes beingespecially adapted for printing purposes, said stable leuco compoundbeing stable to air and oxygen, diflicultly soluble in alkali andyielding prints in the usual wayv but also with a considerably smallerquantity of a case of

